An arrangement of this type is known for example from DE 10 2011 120 152 A1. For rotation of the channel nozzle the purge hose supporting it is twisted as a whole. For this purpose, in the known arrangement a hose holding device formed as a coiler provided for holding a purge hose supply is rotated around an axis parallel to the longitudinal axis of the purge hose phasing out. For this purpose, the coiler is fixed to the rear of a carrier vehicle by means of a pivot joint and twistable by means of a driving mechanism. All supply lines allocated to the coiler as well as the purge water line must be lead centrically through the pivot joint. This proves to be very complex and susceptible to errors. Another disadvantage of the known arrangement is that for carrying out a rotation of the channel nozzle, the purge hose supporting it must be rotated as a whole over its entire length which has an unfavorable effect on the achievable precision. In this connection one has to assume that the purge hose charged with high pressure purge water presents a small but not entirely negligible torsion spring property so that a certain twisting occurs during rotation of the purge hose with increasing length which makes a precise rotation of the channel nozzle difficult, and which therefore can lead to errors regarding the angle of rotation. Thus, the known arrangement turns out to be not simple, trouble-free and precise enough.
DE 20 2012 011 773 U1 shows a purge hose with sections connected with each other via coupling. The coupling contains a housing element and an engagement element engaging into the housing element with the engagement element being formed as a hollow sphere element to which a supporting spherical cap is attributed provided on the housing in order to permit mutual movability of the two purge hose sections around movement axes extending transverse to the flow axis. In direction of rotation around the purge hose axis the two elements of the coupling unit are locked against each other. A rotation around the purge hose axis is therefore transmitted from the rear hose section to the front hose section. Also in this known arrangement, for rotation of the channel nozzle the purge hose must therefore be twisted as a whole which leads to the disadvantages regarding construction, precision and susceptibility to failure already mentioned above.
On this basis, it is an objective of the present invention to improve a device of the type mentioned above with simple and cost-effective means such that not only a simple and cost-effective construction is achieved but also a precise mode of operation with a low rate of failure is guaranteed.